Define "large" amount of circuitry. A boost regulator could get you up to your required voltage fairly efficiently, but that does take some know-how.
A better solution might be to put several batteries in series, which adds voltage linearly. Three batteries in series gets you 11.8V; then you can use an LM317 to regulate that to 9V or whatever you need.
EDIT: I agree with Marco. Use standard 18650 cells. Three of those will get you 10.8V, and chargers for them are cheap.